Safing and arming device

ABSTRACT

In a weapon subject to a sequence of high acceleration followed by high spin and including a detonator and an explosive charge; the improvement comprising a barrier located between the detonator and explosive charge to normally form an obstruction to prevent accidental detonation of the explosive charge by the detonator. Mechanical locking means are provided to lock the barrier in place, comprising a spirally wound ribbon, a pair of pins restraining the outer surface of the ribbon to prevent premature unwinding, and a pair of superimposed anti-friction balls mounted on a hub portion of the ribbon, the upper ball being seated in an extension portion of the barrier. When the weapon is fired from a gun, the high acceleration will remove the pins and allow the ribbon to unwind. Upon unwinding the entire ribbon, the balls will be released and the barrier under the action of spin, will be removed to provide an unobstructed path between the detonator and explosive charge.

This invention relates to a safing and arming (S & A) device which formsan integral part of a small cailber (or even high caliber) explosiveshell fired at high velocity from an internally-rifled gun.

The invention is primarily intended for use in conjunction withrapid-fire small caliber weapons. This being the case, the main factorsmotivating this invention are:

(a) The very small volume available for insuring the safing and armingfunction; and

(b) The requirement that the resulting device be simple and cheap tomanufacture.

BACKGROUND OF THE INVENTION

An outstanding disadvantage of present safing and arming devices is thatthey usually require a source of electrical power, such as a battery,which through shelf-age may become inoperable; therefore, making thedevice undependable as well as adding to size and weight of the device.

Another disadvantage is that such devices often are not dependable toassure against accidental explosion before the shell is a safe distanceaway from the firing gun.

An object of the present invention is to provide a novel safing andarming device which will overcome the above-named disadvantages.

A more specific object of the invention is to provide a safing andarming device which requires no electrical energy for its operation;therefore can be made extremely small in size and light in weight, aswell as relatively inexpensive to manufacture.

Another object of the invention is to provide a novel safing and armingdevice which is operable only after a predetermined accelerationfollowed by a predetermined amount of spin of the shell carrying thedevice before detonation of the explosive charge; therefore insuring ahigh degree of safety.

BRIEF DESCRIPTION OF THE DRAWING

Other objects and advantages of the invention will become more apparentfrom a study of the following description taken with the accompanyingdrawing wherein:

FIG. 1 is a vertical cross-sectional view taken along line 1--1 of FIG.2 of a safing and arming device embodying the present invention; and

FIG. 2 is a top sectional view thereof taken along line 2--2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring more particularly to FIGS. 1 and 2, numeral 1 denotes a casingfor housing an assembly of fuze parts, together with a detonator 2.Above the casing 1, there is an explosive charge 3 contained in acylindrical portion of the assembly.

The present invention is specifically directed to the safing and armingdevice forming an integral part of a small caliber explosive shell,which device is contained in the housing consisting of a base 4a and ofa cover 4b. The device comprises a barrier 5 for obstructing the pathbetween detonator 2 and explosive charge 3, which barrier is supportedon a hub 6, around which is wound a spiral ribbon 7, preferably ofmetal, of a predetermined number of turns depending upon the minimumdistance from the gun at which detonation is permitted to take place.

Set-back pins 8 and 9 in the positions shown, that is, contacting theouter surface of ribbon 7, will prevent unwinding of the ribbon. Barrier5 has an integral extension 5a which has a surface of an appropriateshape for seating an anti-friction ball 11 which rests on top of ananti-friction ball 12. Both balls 11 and 12 normally rest in a groovewithin the hub 6, with the ball 11 restrained by the ball 12 which, inturn, is restrained by the ribbon 7, thus locking the barrier 5 inplace. A membrane 10 completes the enclosure of the spiral ribbon andassociated parts, so that in the normal position, shown in FIG. 1,barrier 5 prevents any accidental setting off by the detonator 2 of theexplosive charge 3. That membrane or foil may be manufactured either asa separate part pressed against the bottom of the housing, as shown inFIG. 1, or as an integral part of the housing base 4a.

In operation, when the shell having the above-described safing andarming device is fired from a gun which is internally rifled, it will beejected through the muzzle of the gun at high velocity and high spinbecause of the internal rifling. Thus, under the influence of highacceleration and high initial set-back, the set-back pins 8 and 9 willpuncture holes in membrane 10 and will be forced downwardly into holes13 and 14 in either tubes or in a solid mass below membrane 10. When theset-back pins 8 and 9 move into holes 13 and 14, the spin will move themradially outwardly against outermost walls of the pockets or holes 13and 14, since the diameters of holes 13 and 14 are larger in an outwarddirection than those of pins 8 and 9, as will be apparent in FIG. 1.

This will prevent return of the pins back into their normal or upperposition as might otherwise happen later. Thereupon, the ribbon 7, byvirtue of spin of the projectile and S & A device, will unwind, and uponcomplete unwinding thereof, and with the ribbon out of the way, ball 12followed by ball 11, under the action of spin, will move radiallyoutwardly into the space previously occupied by spiral ribbon 7. Sincethe center-of-gravity of the barrier 5 is offset outwardly from the spinaxis, the barrier will be moved, by spin, completely away from the pathexisting between detonator 2 and the high explosive charge 3, therebyallowing detonation of the charge because of removal of the obstacleprovided by barrier 5. For example--one layer of coil may unwind or peeloff while the unit makes one revolution, equivalent to a travel equal toabout 30 calibers. The larger the number of turns, the greater the safearming distance away from the firing gun.

It should be noted that the present invention is limited in use torounds that are fired with high acceleration from an internally rifledgun so as to provide the round or projectile with spin. Therefore, it isnot applicable to ordinary mortar shells or rockets.

Thus it will be seen that I have provided a safing and arming unit 4which may be of very small size, since it requires a small number ofsimple parts, and which is responsive to the combination of highacceleration or set-back followed by high spin to remove the barrier andpermit the setting off of the explosive charge by the detonator, therebyassuring that the explosive charge will not be accidentally detonatedduring storage, handling, transportation or even after firing until theshell is at a safe distance from the firing gun.

While I have illustrated and described a single specific embodiment ofmy invention, it will be understood that this is by way of illustrationonly and that various changes and modifications may be contemplated inmy invention within the scope of the following claims.

I claim:
 1. In a weapon subject to a sequence of acceleration followedby spin, including a detonator and an explosive charge, the improvementcomprising a barrier located between said detonator and explosive chargeto normally form an obstruction to prevent accidental detonation of saidexplosive charge by said detonator, said barrier having acenter-of-gravity offset radially outwardly of the axis of spinsufficiently so as to be completely removable laterally as anobstruction between said detonator and explosive charge, mechanicallocking means devoid of a source of electrical power for its operationfor normally locking said barrier in place to provide said obstruction,said mechanical locking means including a spirally wound ribbon wrappedaround said barrier, restraining means normally engaging an outersurface of said spirally wound ribbon to prevent premature unwinding ofsaid ribbon, said restraining means being responsive to saidacceleration to disengage said ribbon and permit unwinding thereof as aconsequence of said spin, said mechanical locking means also comprisinglocking elements restrained by the inner leaves of said spirally woundribbon and normally locking said barrier in place, said locking elementsbeing responsive to a predetermined number of spins to unlock and removesaid barrier laterally and provide an unobstructed path between saiddetonator and explosive charge.
 2. A weapon as recited in claim 1wherein said restraining means comprises a pair of pins locateddiametrically opposite the outer surface of said spirally wound ribbonand held in place by a thin foil normally engaging one end of said pinsand which can be punctured by said pins under high acceleration or setback to remove the pins from restraining engagement with said outersurface of said ribbon.
 3. The weapon recited in claim 2 together withmeans for receiving said pins after puncturing said foil, comprisingtubular receptacles of substantially larger diameter than said pins in aradially outward direction from the spin axis.
 4. A weapon as recited inclaim 1, wherein said locking elements comprise a pair of superimposedanti-friction balls, an integral finger portion of said barrier seatinga top portion of the uppermost superimposed anti-friction ball.